1. Field of the Invention
This invention relates to a method for sharpening knives used in wood chippers such as a rotatable disc type in which the disc carries a plurality of circumferentially spaced radial knives alongside chip-discharge openings through the disc.
2. Prior Art
Wood chippers having rotatable cutters, or drums, or rotatable chipping discs fitted with double-edged knives are known in the art.
A single resharpening of the knife blade, involving the removal of material from one or both of the edge surfaces forming the wedge cutting edges of a double-edged knife is often the only reshaping or resharpening of a knife blade before it is discarded.
One aspect of the geometry of chipper knives is that knives having a large wedge angle, i.e., the angle between the two surfaces converging to the cutting edge, remain sharper longer and therefore are more popular. However, the larger wedge angles are more likely to cut a chip by shearing the chip from the incoming material rather than by cleavage. More force is required to sever chips by shearing than by cleavage, and thus more power is required to operate a disc chipper having knives with larger wedge angles.
Another problem is the penetration of chip particles between the knife and the knife holding means beneath the knife, typically a counter knife, that can cause excessive pressure on the knife which may bend it outwardly sufficiently to hit the anvil.